It is the last night of campaigning in Spain's northeast region of Catalonia. Separatists are holding a vote on independence on Sunday. It is a vote that the Spanish government has promised to stop. Madrid has sent thousands of police to Catalonia from all over Spain. Reporter Lauren Frayer joins us now from the Catalan capital of Barcelona. Hey there.

LAUREN FRAYER, BYLINE: Hi, Kelly.

MCEVERS: So what's it like in Barcelona tonight?

FRAYER: It's surprisingly festive. I mean separatist campaigners are setting up a huge stage for an all-night concert and political rally. Farmers have driven their tractors into the city to join in. Catalans say they're confident that they will be able to hold this vote. They showed off ballot boxes to the media today.

And yet at the very same moment back in Madrid, the Spanish government was issuing a statement saying the whole thing will not happen, that it's unconstitutional. Thousands of extra police are here. All over the country, there were these goodbye parades for local police shipping off to Catalonia. And so emotions are running high across the country. Lots of Spaniards are really upset about the possibility of Catalonia breaking away.

MCEVERS: The Spanish government has arrested separatist leaders, and police have already confiscated ballots. Is that affecting how people are going to vote?

FRAYER: It's important to remember that Catalans have been divided over this. The most recent polls a few weeks ago showed about a 50-50 split for and against independence, though a vast majority want the right to vote on the issue. But all of these arrest raids that you mentioned may be galvanizing undecided voters. And here's one such voter. His name is Oscar Lopez. He's 29 years old, and he works for the Barcelona City Hall.

OSCAR LOPEZ: (Speaking Spanish).

FRAYER: He says at first, he was going to vote no against independence, and now he's thinking of voting in favor of independence. And it's because he thinks the Spanish prime minister, Mariano Rajoy, and his central government have handled this really poorly.

MCEVERS: So it sounds like kind of a standoff between Barcelona and Madrid. What do you think's going to happen on Sunday?

FRAYER: Well, police have been ordered to surround the public schools and empty them completely by 6 a.m. local time Sunday. These are more than 2,300 public schools that are being used as polling stations. Parent-teacher associations meanwhile say they'll barricade themselves inside, and many college students are already occupying university buildings in Barcelona. Here's what it sounded like earlier today.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED CROWD: (Chanting in Spanish).

FRAYER: Those are Catalan teachers at a pro-independence rally. And you can hear them shaking sets of keys in the air. They're saying these are the keys to the public schools, and they're saying that they hold the keys, not the police.

MCEVERS: Wow. So if the yes votes win, if this region votes for independence, what happens then?

FRAYER: Well, anti-independence parties are calling on their supporters to stay home. So we could have a situation where only a third of Catalans or even less than that vote. And yet the regional government declares independence based on that. They have said they'll make that declaration within 48 hours. It may fall on deaf ears. No country in the world has said it would recognize an independent Catalonia. Most people are hoping this leads to negotiations rather than, you know, a physical confrontation, but emotions are really high on both sides, and it's frankly hard to imagine anyone backing down.